package com.temp.client.foundation.widget.input.fieldsupport;

import com.google.gwt.event.dom.client.*;
import com.google.gwt.event.shared.*;
import com.temp.client.foundation.widget.input.support.*;
import com.temp.client.foundation.widget.input.support.events.*;
import com.temp.shared.utils.*;

public class InputWidgetChangeFilter<T> implements InputWidgetValueAdapter<T> {
    protected final NonDomHandlerManager<ChangeHandler> handlerManager;
    protected final InputWidgetValueAdapter<T> delegateTo;
    protected T baseNotChangedValue;
    protected boolean isChanged;

    public InputWidgetChangeFilter( InputWidgetValueAdapter<T> delegateTo ) {
        handlerManager = new NonDomHandlerManager<ChangeHandler>( this );
        this.delegateTo = delegateTo;
        baseNotChangedValue = delegateTo.getValue();
        delegateTo.addChangeHandler( new ChangeHandler() {
            @Override
            public void onChange( ChangeEvent event ) {
                checkForChange();
            }
        } );
    }

    public HandlerRegistration addFilteredChangeHandler( ChangeHandler handler ) {
        return handler == null ? null : registerChangeHandler( handler );
    }

    @Override
    public HandlerRegistration addChangeHandler( ChangeHandler handler ) {
        return delegateTo.addChangeHandler( handler );
    }

    @Override
    public T getValue() {
        return checkForChange();
    }

    @Override
    public void setValue( T value ) {
        delegateTo.setValue( value );
        baseNotChangedValue = delegateTo.getValue();
        setChanged( false );
    }

    public T getBaseValue() {
        return baseNotChangedValue;
    }

    public void setValueAsUser( T value ) {
        delegateTo.setValue( value );
        checkForChange();
    }

    public boolean isChanged() {
        return isChanged;
    }

    protected T checkForChange() {
        T curValue = delegateTo.getValue();
        setChanged( !ObjectUtils.areEqual( baseNotChangedValue, curValue ) );
        return curValue;
    }

    protected void setChanged( boolean newChangedState ) {
        boolean curChangedState = isChanged;
        isChanged = newChangedState;
        if ( curChangedState != newChangedState ) {
            notifyChangeHandlers();
        }
    }

    protected void notifyChangeHandlers() {
        handlerManager.fireEvent( new NonDomChangeEvent() );
    }

    protected HandlerRegistration registerChangeHandler( ChangeHandler handler ) {
        return handlerManager.addHandler( handler );
    }
}